One prior-art device for lapping various components (U.S. Pat. No. 3,968,598) is known to comprise an abrasive tool and an appliance aimed at building up a holding-down force within the cutting zone, said appliance having a housing with a guideway, wherein a poppet sleeve carrying a spindle is free to reciprocate so as to translate the holding-down force to the abrasive tool. Feed motion is effected by means of a hand-driven toggle-arm mechanism.
The workpiece-to-abrasive-tool holding-down force in the aforediscussed device is constant and independent of the abrasive tool profile. Such a construction results in that the workpiece being machined "traces" the profile of the tool working portion, which makes it impossible to correct the geometrical shape of the tool working surface in the course of machining and thereby fails to provide high machining accuracy without a separate operation of additional tool dressing.
One state-of-the-art machine for grinding and polishing flat and plain workpiece surfaces (SU, A, No. 679,375) is known to comprise an abrasive tool and an appliance for creating a holding-down force within the machining zone, said appliance having a housing provided with guideways, wherein poppet sleeves carrying spindles are free to reciprocate so as to translate the holding-down force to the abrasive tool. Besides, each of the poppet sleeves has its own spring.
In the above-described machine the workpiece-to-abrasive-tool holding-down forces are applied independently of one another. Therefore there occurs "tracing" of the tool working surface profile by the workpieces being machined, which also makes it impossible to correct the geometrical shape of the tool working surface in the process of machining and thereby fails to provide high machining accuracy without a separate operation of additional dressing.
One more machine for grinding and lapping flat and plain surfaces (U.S. Pat. No. 3,110,988) is known to comprise an abrasive tool and an appliance for establishing a holding-down force. Special dressing rings are freely placed on the abrasive tool surface with a possibility of rotating in the opposite directions.
Since the holding-down force is established within the machining zone by virtue of own weight of the dressing rings there occurs "tracing" of the profile of the tool working surface by the dressing rings, which precludes elimination of camming action of the macroirregularities on the abrasive tool working surface, in particular, waviness (when the wave length exceeds the dressing ring diameter) and hence makes it impossible to correct the geometrical shape of the tool working surface in the course of workpice machining which in turn fails to provide high machining accuracy without a separate operation of additional dressing.
The closest to the machine of the invention is a device for grinding flat and plain surfaces (SU, A, No. 1; 104,762). The device comprises an abrasive tool and an appliance for establishing a holding-down force within the machining zone, said appliance having a housing with guideways, wherein poppet sleeves carrying spindles are free to reciprocate in order to translate the holding-down force to the abrasive tool and the feed mechanism provided on the housing. The spindles are secured, with their stationary portions, on a rigid cross-arm. With such a construction of the appliance for establishing a holding-down force, all spindles carrying the work-pieces being machined are made simultaneously to withdraw from the abrasive tool upon contacting of the components of one of the spindles with protruding irregularities on the abrasive tool working surface. As a result, the forces applied to each of the spindles are added together to give a total value of the force applied at the place of contact. Thus, a possibility is provided of correcting the grinding wheel geometric shape. However this affects adversely both workpieces' machining accuracy und quality of their surface finish, since the workpieces withdrawn from the abrasive tool sustain impact loads upon cyclic getting in contact with said tool, which entails disturbance of the geometric shape of the machined surface, e.g., flatness, as well as its mutilation, such as spalling, broken-off egdes and even complete destruction of the whole workpieces, this being especially the case when machining thin workpieces.
Moreover, increased fitting clearances in the guideways of the poppet sleeves might lead to a deteriorated geometric shape of the abrasive tool rather than its improvement, e.g., disturbed flatness in a radial direction (the so-called "tilt" of a grinding wheel).